The present invention relates to an image forming apparatus.
Image forming apparatuses often use a cleaner blade in order to remove the toner on an image carrier. As described in JP H8-63071 A, when the cleaner blade is kept in pressure contact with the image carrier used for successive monochrome printing, toner coagulates at the top end of the cleaner blade, thereby causing a problem of degraded performance of the cleaner blade.
Accordingly, in the image forming apparatus in JP H8-63071 A, the cleaner blade is temporarily released from the image carrier at intervals between images during monochrome printing, so that coagulations at the top end of the cleaner blade are dropped off by vibration.
Four cycle image forming apparatuses have conventionally conducted color printing by rotating an intermediate transfer belt four turns, so that toner images of four colors are primarily transferred in superimposition on top of each other, and that the toner images of four colors are secondarily transferred onto recording paper collectively. After the secondary transfer is completed, the cleaner blade is pressed to the intermediate transfer belt in order to remove the toner remaining on the intermediate transfer belt, and then the cleaner blade is again released at the time of the next image formation.
In recent years, in order to achieve downsizing and cost reduction of image forming apparatuses, there have been being produced image forming apparatuses which use intermediate transfer belts lacking in a satisfactory level of smoothness and releasability, as well as inexpensive toner cartridges incapable of stirring and homogenizing the internal toner. In these image forming apparatuses, even in color printing in which the cleaner is released once every four rotations, toner or external additives of the toner or the like may coagulate at the top end of the cleaner blade, resulting in degraded performance of the cleaner blade, which may lead to occurrence of a phenomenon called filming that the external additives of the toner are deposited like a film on the intermediate transfer belt, thereby causing degraded image quality.
For downsizing of image forming apparatuses and improvement in their printing speed, some image forming apparatuses have an intermediate transfer belt with a shortened circumferential length so as to decrease the distance between images. In such image forming apparatuses, the intermediate transfer belt needs to be additionally rotated to perform pressing and releasing of the cleaner blade, and excessively increased press and release operations of the cleaner blade would cause a problem of lowered printing speed.
Further, excessive press and release operations of the cleaner blade may make toner float in the image forming apparatus and tend to contaminate the inside of the apparatus, which may deteriorate the maintenanceability and cause trouble and degradation of image quality.